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arXiv · 2105.04563

Improved Standard-Model prediction for $\pi^0\to e^+e^-$

Martin Hoferichter·Bai-Long Hoid·Bastian Kubis·Jan Lüdtke
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Abstract

We present an improved Standard-Model (SM) prediction for the dilepton decay of the neutral pion. The loop amplitude is determined by the pion transition form factor for $\pi^0\to\gamma^*\gamma^*$, for which we employ a dispersive representation that incorporates both space-like and time-like data as well as short-distance constraints. The resulting SM branching fraction, $\text{BR}[\pi^0\to e^+e^-]=6.25(3)\times 10^{-8}$ , sharpens constraints on physics beyond the SM, including pseudoscalar and axial-vector mediators.

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Martin Hoferichter, Bai-Long Hoid, Bastian Kubis, Jan Lüdtke. 2021-05-10. Improved Standard-Model prediction for $\pi^0\to e^+e^-$. https://doi.org/10.1103/physrevlett.128.172004

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